Where to Buy Retatrutide: 7 Purity and Identity Checks on a Drug No Regulator Has Approved

Retatrutide has 1,150 independent lab tests on this platform and one published trial: a 338-person phase 2. It has never been approved, so it has never been in shortage, so no compounding route has ever existed for it.

Retatrutide sits in the weight loss and metabolic peptides category as its most-tested and least-evidenced compound. The evidence picture is in retatrutide: the 24.2% weight-loss figure comes from a 338-person phase 2 trial; this page is about the vial and the law around it. For per-injection volume there is a retatrutide calculator.

What is retatrutide, and why does source quality matter?

Retatrutide is a triple agonist at the GIP, GLP-1 and glucagon receptors, molecular weight 4,731.0 g/mol, formula C₂₂₁H₃₄₂N₄₆O₆₈, development code LY3437943. Source quality matters here in an inverted way: this platform holds 1,150 independent lab tests of a drug with no published phase 3 result and no approval anywhere. The supply chain is better characterised than the medicine, and a purity figure is not evidence that the drug works.

Adding glucagon receptor agonism to the GIP/GLP-1 combination is intended to raise energy expenditure alongside appetite suppression, which is a different lever from eating less. The clinical case for it rests on one trial: Jastreboff et al., New England Journal of Medicine 2023;389(6):514–526, phase 2, n=338, 48 weeks, −24.2% at 12 mg against −2.1% on placebo.

The CAS point is small on its own and telling in aggregate. PubChem's record does not expose a CAS number for retatrutide, and the number circulating on vendor pages comes from secondary sources. This is a compound where much of what is quoted as specification traces to nowhere authoritative, which is worth knowing before you treat a vendor's spec sheet as a document rather than a claim.

The identity risk is concrete and it has a number attached. At 4,731.0 g/mol retatrutide sits 82 daltons below tirzepatide at 4,813.0, and the two are acylated multi-agonist peptides of similar size sold through the same shops. See mass spectrometry for peptides for what an identity test establishes that a purity figure cannot.

What is the regulatory status of retatrutide?

Retatrutide is not approved anywhere we could verify. As of August 2026 it is absent from FDA's drug application database and from FDA's novel approvals lists for 2025 (46 drugs) and 2026 (30 drugs, current through 5 August 2026). Because it has never been approved it has never been in shortage, so no compounding route has ever existed for it. A pre-approval expanded access programme, NCT07629401, is listed as AVAILABLE and runs through physicians.

That last chain is the single most important legal fact on this page, and it is structurally different from the answer for its siblings. Semaglutide and tirzepatide were approved drugs that went into shortage, which is what briefly permitted 503A and 503B compounding of essentially-a-copy versions; both shortages are now resolved and both routes are closed. Retatrutide never entered that framework at all, because the framework begins with an approved product. Anyone offering "compounded retatrutide" is describing something that has never been lawful — see compounding pharmacy versus research peptide.

Retatrutide does not appear on FDA's compounding lists. We enumerated both tables on the page current 22 April 2026: no GLP-1, GIP, glucagon or amylin agonist is on either. That absence carries no permission whatsoever. Retatrutide sold outside a clinical trial or an expanded access programme is an unapproved new drug, and FDA "has warned companies that have illegally sold unapproved drugs... falsely labeled 'for research purposes' or 'not for human consumption.'"

Expanded access is the one legitimate non-trial route, and it does not run through a shop. ClinicalTrials.gov carries NCT07629401, "Pre-approval Expanded Access of Retatrutide," with status AVAILABLE. Expanded access — sometimes called compassionate use — lets patients receive an investigational drug outside a trial. It is not approval, and it operates through physicians and the sponsor. For what that means practically, see do you need a prescription for retatrutide.

On sport, retatrutide is not named on the WADA 2026 Prohibited List, and no GLP-1 class entry exists. But the S0 catch-all prohibits substances "with no current approval by any governmental regulatory health authority for human therapeutic use," expressly including "drugs under pre-clinical or clinical development." Retatrutide holds no approval anywhere, so on the plain text S0 applies. That is our reading rather than a published WADA ruling, and an athlete should seek a determination.

Two published items bear directly on retatrutide sold outside the clinic. Giblin et al. (Diabetes, Obesity and Metabolism, January 2026) describe the four-trial TRIUMPH programme and more than 5,800 participants, with no results published. And Piatkowski, Craven, Cornell & Ferris report on the composition and labelling accuracy of products sold as retatrutide in Australia (Drug and Alcohol Review, September 2026, DOI 10.1111/dar.70231). We verified that citation and could not obtain the abstract, so we are not characterising what it concludes — but it is the closest peer-reviewed analogue to what this platform does, and anyone buying retatrutide should read it directly.

How do you tell retatrutide from tirzepatide?

Retatrutide and tirzepatide are 82 daltons apart: 4,731.0 g/mol against 4,813.0 g/mol. A mass spectrometer resolves that gap instantly and an HPLC purity figure does not address it at all, because purity measures the proportion of a sample that is the main peak rather than which molecule that peak is. On a compound sold without approval anywhere, the identity test is the one check that cannot be substituted.

The two are easy to confuse for reasons that have nothing to do with fraud. They are both acylated multi-agonist peptides in the same weight range, they are stocked by the same shops, they are titrated over similar milligram ranges, and they are frequently listed side by side in the same catalogue with near-identical descriptions. A mislabelled vial does not require anyone to have intended it.

So ask for the mass, not the percentage, and ask for it on your batch. A certificate showing a purity percentage with no mass result tells you that whatever is in the vial is mostly one thing. It does not tell you which of the two it is, and on a drug titrated in 1–2 mg steps against one titrated in 2.5 mg steps, that distinction changes the dose as well as the molecule. How to read peptide lab test results walks through both traces side by side.

7 things to check before ordering retatrutide

Seven checks apply to retatrutide, and one of them is not about the vial at all. Mass spectrometry at 4,731.0 Da, HPLC read against a 99.67% platform average from 1,150 tests, fill accuracy against a −4% to +22.5% variance range, the salt form, a certificate from a laboratory with a retatrutide record, and a price check against an $8.00/mg median. The seventh is knowing what none of those tests can tell you.

1. Mass spectrometry at 4,731.0 Da. This is the check that separates retatrutide from tirzepatide at 4,813.0, and it is the only one that does. Insist on a batch-matched result rather than a specimen certificate showing a mass from some earlier lot.

2. HPLC purity read against a narrow known band. Retatrutide averages 99.67% across 1,150 tests on this platform, with individual results running 99.52% to 99.98%. That is an unusually tight distribution, which makes it a useful benchmark: a result outside it is informative in a way that "above 98%" never is.

3. Fill accuracy, measured rather than assumed. Quantity variance on record runs −4% to +22.5%, with most results within ±5%. Retatrutide is titrated in 1–2 mg steps, so a 22.5% overage is a step-and-a-half you did not choose. See why 10 mg isn't 10 mg.

4. The salt form, stated on the certificate. The salt form determines what you are actually weighing when you reconstitute a labelled 10 mg vial. A certificate that omits it has left out a variable that changes every dose you draw from that vial.

5. The CAS number the vendor prints, read as a signal rather than a specification. PubChem exposes no CAS for retatrutide, and 2381089-83-2 is a number we could not verify against a chemical registry. A vendor presenting it as settled specification is telling you their spec sheet was assembled from other vendors' spec sheets — see red flags in peptide certificates of analysis.

6. Who tested it, and what they left off. The 1,150 results here come from Janoshik, Freedom Diagnostics, Bioviridian, Kovera and ILS. Endotoxin is the line most often missing on this compound — LAL results are rarely reported for retatrutide, and an absent result means the batch was not tested rather than that it passed. Peptide endotoxin testing and LAL interpretation covers how to read one.

7. What no test on the vial can establish. The median price is $8.00/mg and the market is well supplied, and neither fact is a quality signal or a safety signal. A perfect certificate confirms that a vendor sold the correct molecule at the stated quantity. It says nothing about efficacy, dosing, long-term safety, or how a phase 2 result will hold up in phase 3 — and the only route to this compound that comes with a clinician attached is NCT07629401.

Where does retatrutide rank on Peptigrity's lab test database?

The Purity Index records retatrutide at 99.67% average across 1,150 independent tests (verified August 2026), the largest test dataset on this platform, from Janoshik, Freedom Diagnostics, Bioviridian, Kovera and ILS, across 230 shops selling. Individual results run 99.52% to 99.98%, and quantity variance runs −4% to +22.5%, with most within ±5%. What those tests cannot show is efficacy, dosing, long-term safety, or how a phase 2 result will hold up in phase 3.

Stop and consider that number. Eleven hundred and fifty independent lab tests of a drug that has never been approved and has no published phase 3 result. That points somewhere uncomfortable: purity data has become a substitute for clinical evidence in how this compound is discussed. High-quality manufacture of a molecule with 338 people of phase 2 data behind it is high-quality manufacture of a molecule with 338 people of data behind it.

Peptigrity's platform currently tracks 530 shops and 11,852 independent lab tests across 118 peptides, with 1,283 community reviews (verified August 2026), and trust scores weight community reviews and independently verified HPLC purity equally at 50% each, with no financial relationship influencing the ranking. Individual results are searchable in the lab test database, and shop-by-shop detail sits on the retatrutide compound page. For the adverse-event picture as reported so far, see retatrutide side effects.

Retatrutide price data shows 15 shops in stock, median $8.00/mg, lowest $2.33/mg on a 40 mg vial (verified 31 July 2026), across 53 compared offers with vial prices from $24.99 to $500.00. Those figures exclude shipping, taxes and customs, coupon codes, bulk tiers, multi-vial kits and account-gated pricing.

Read that spread against the evidence rather than against the market. A tighter price band than most compounds on this platform, on a molecule with one published trial behind it, describes a well-organised supply chain rather than a well-evidenced drug.

The trial that would settle this is not a testing study. On retatrutide, uniquely in this cluster, the supply side is the part that has been measured and the clinical side is the part that has not.

That fifth row deserves more attention than it gets. Glucagon receptor agonism adds nausea and vomiting risk on top of an already emetogenic class, and the phase 2 abstract does not tell us how many people left the trial because of it.

Frequently Asked Questions

What purity standard should retatrutide meet?

Retatrutide averages 99.67% across 1,150 independent tests on this platform, with individual results between 99.52% and 99.98% — the tightest distribution of any compound in this cluster. Treat anything outside that band as worth a question rather than as a marginal pass. And keep the purity figure in proportion: it establishes that a vendor sold the right molecule, not that the molecule has been shown to work.

How much does retatrutide cost?

Median $8.00 per milligram, lowest $2.33 per milligram on a 40 mg vial, across 53 compared offers from 15 shops in stock (verified 31 July 2026), with vial prices from $24.99 to $500.00. Per-milligram cost falls with vial size, from an $11.50 median in the 5–10 mg tier to $6.67 in the 30–65 mg tier. Those figures exclude shipping, taxes and customs, coupon codes, bulk tiers, multi-vial kits and account-gated pricing.

Is retatrutide legal, and can it be compounded?

It is not approved anywhere we could verify, and it cannot be compounded. The 503A and 503B route permits copying an approved drug only while that drug is in shortage; retatrutide has never been approved, so it has never been in shortage, so the route has never applied. Sold outside a clinical trial or expanded access, it is an unapproved new drug.

How do you verify retatrutide is not tirzepatide?

Mass spectrometry, on your batch, showing a mass near 4,731.0 Da rather than 4,813.0. The 82-dalton gap is trivial for the instrument and invisible to an HPLC purity figure, which reports how much of the sample is the main peak without identifying it. A certificate with a purity number and no mass result has not answered the question.

How is retatrutide dosed, and in what steps?

The phase 2 trial tested 1, 4, 8 and 12 mg, with −8.7%, −17.1%, −22.8% and −24.2% at 48 weeks respectively, and titration proceeds in 1–2 mg steps. That is trial protocol rather than an approved schedule, because no approved schedule exists. For reconstitution volume and per-injection units, use the retatrutide injection guide alongside the retatrutide calculator.

Does 1,150 clean lab tests mean retatrutide is safe?

No. Those tests establish that vendors are broadly selling the correct molecule at roughly the stated quantity. They say nothing about efficacy, dosing, long-term safety, or how a 338-person phase 2 result will hold up in a phase 3 programme enrolling more than 5,800 participants — all of which remain open, and the discontinuation rate at effective doses is not reported in the phase 2 abstract.

Browse the weight loss and metabolic peptides category, or our complete peptide guide with 118 compounds (verified August 2026). For per-injection volume, use the retatrutide calculator alongside the reconstitution calculator. Compare shops through independent lab tests and community-verified shop reviews.

This article is for educational and informational purposes only and does not constitute medical advice. Peptides discussed may be investigational compounds not approved by the FDA (or equivalent regulators in your jurisdiction) for human use. Always consult a qualified healthcare provider before using any peptide or research compound. Peptigrity is an independent review platform and does not sell, endorse, or recommend specific products or vendors.